The present invention relates to water filtration devices, which include a cyst-reducing water filter capable of reducing parasites and other impurities in drinking water and yet capable of delivering a substantial water flow rate at relatively low (gravity-assisted or gravity-flow) water pressures. While the invention may be used in other types of water filtration devices, it is especially suited for use in gravity-flow water carafes, and will be particularly described in that connection.
Until recently, water filter carafes of commercially available design have not been capable of parasite reduction, which requires much finer filtration. Nor have they been effective for the significant reduction of organic chemicals, pesticides and insecticides, which requires more carbon. While such additional removal attributes are desirable, they have not been technically feasible in the filter sizes required and at the filter cost currently available in the market. In addition to the concerns about drinking water taste and odor, consumers are beginning to be more concerned with the quality of drinking water, thus increasing the demand for gravity-flow filter carafes. This is because such water filter carafes are relatively low in cost and operate in a simple manner. Water from a tap is simply poured into the top of the filtration unit and is allowed to flow through a replaceable filter cartridge to a treated water reservoir for later use.
A typical commercially available cyst-reducing water filter cartridge consists of a filter housing which contains a packed bed mixture of ion-exchange resin for the removal of unwanted ions, for example, lead, copper, and hard water ions, as well as carbon granules for the removal of adsorbable/catalyzable constituents such as chlorine and undesirable tastes and odors. Further, the filter housing contains a high surface area cyst-reducing filter element that is capable of removing harmful parasites and dirt that are present in water from a municipal water source. Without the cyst-reducing filter element, the housing containing the packed bed mixture that is commercially available for use in gravity-flow water carafes typically have physical volumes on the order of 165 cm3 (10 in3). This suggests that a filter incorporating the additional cyst function using the current designs would require more volume than that mentioned above. Gravity cyst-reducing filters should be able to achieve the production of a reasonable quantity of filtered water in a reasonable time, preferably, approximately 1 liter in less than 12 minutes.
Although filter designs and materials capable of cyst reduction exist, significant problems remain concerning appropriate methods and designs for incorporating such filters into effective, gravity-assisted water carafe purification systems. In order to sustain adequate flow rates throughout the life of the filter, the design must be such that air entrapment within the filter must be minimized. In addition, the design should be such that either a hydrophilic or a hydrophobic microporous cyst-reducing filter element can be used to sustain maximum flow rates. Maximum flow rates are achieved when water has displaced the air in the filter pores. This displacement of air from the pores and its replacement with water can be referred to as priming and when this displacement process is complete the filter is referred to as being in the primed state. The maximum flow rate is achieved when the filter element remains in the primed state. The filter cartridge design should allow the cyst-reducing filter element to remain in the primed state, that is, fully submerged at all times. The inventive combination of a filter cartridge design which allows both proper cartridge venting and which keeps the filter primed is essential to a successful filter.
A design in which only one of the two factors is present will reduce flow. Designs which only allow the filter to remain in its primed state, but which neglect venting promote the development of air locks beneath the packed bed of ion-exchange resin and/or under the cyst-reducing filter element, which significantly diminishes or stops the water flow rate. Air locks can come from two sources, entrapped air bubbles and dissolved air. The tap water out of a faucet that is introduced into the filters is typically less than 55xc2x0 F. Moreover, the tap water usually is directed first through an aerator which mixes air with the water and creates water that is full of bubbles. Some air enters the filter cartridge in the form of these bubbles, which penetrate into the filter cartridge and can coalesce with other bubbles to form larger bubbles which cannot get back out, thus, forming air locks within the cartridge. Secondly, air can enter and move through the cartridge in the form of dissolved oxygen and nitrogen. As the water temperature reaches room temperature or above the temperature of the original tap water, the solubility of these two gases decreases and the gases come out of the water, thus, forming air locks in the filter cartridge. Furthermore, designs which allow venting, but do not keep the filter in the primed state do not produce the maximum flow of water through the cartridge.
In light of the foregoing, it is desirable to provide a water filtration device that can provide a reduction of very fine particulate biological cysts and other impurities from drinking water. Also, it is desirable to provide a water filtration device that can deliver substantial volumes of filtered water at relatively low water pressures. In addition, it is desirable to provide a water filtration device that maintains the cyst-reducing filter element in a primed condition and prohibits the development of air locks, thus, providing an adequate filter flow rate. Furthermore, it is desirable to provide a water filtration device that promotes the removal of any air trapped between the packed bed of ion-exchange resin and the cyst-reducing filter element and prevents any water from bypassing the cyst-reducing filter element. Finally, it is desirable to provide a water filtration device that is replaceable and cost effective in the market place.
Accordingly, the present invention is directed to a water filtration device that substantially obviates one or more of the limitations and disadvantages of the related art. The principal advantage of the present invention is the provision of an arrangement which overcomes the limitations and disadvantages of the described prior arrangements. Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the apparatus particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the water filtration device is a replaceable cyst-reducing water filter cartridge for use in a water filter carafe. In accordance with the present invention, the filter cartridge includes a housing that further comprises a top rim, a side surface, a bottom surface, and a cap that is sealingly attached to the top rim, wherein the cap comprises a plurality of untreated water inlet ports. The filter housing further comprises a gooseneck conduit that is connected to a lower region of the filter housing, wherein the gooseneck conduit has at one end a treated water outlet port that opens into the side surface of the filter housing. The filter housing further includes a packed bed of ion-exchange resin that is disposed in the filter housing and a high surface area cyst-reducing filter element that is also disposed in the filter housing. The filter element provides at least 99.95% removal of 3-4 xcexcm particles when tested in accordance with NSF standard 53, Drinking Water Treatment Unitsxe2x80x94Health Effects (September 1997). A bottom surface of the packed bed of ion-exchange resin is in full contact with one side of a bottom screen that is attached at the periphery to the side surface of the housing. The other side of the bottom screen forms a ceiling in a first chamber. The first chamber separates the packed bed of ion-exchange resin from the cyst-reducing filter element. The housing further comprises a second chamber proximate to the bottom surface of the filter housing, wherein the second chamber is in fluid communication with the gooseneck conduit. The housing also includes an air vent conduit that is connected to the upper region of the filter housing, wherein the air vent conduit has an entry end that opens into the first chamber and an exit end that opens to the outside of the housing. The exit end is positioned above the treated water outlet port of the gooseneck conduit and the exit end is further covered with a hydrophobic membrane. In one embodiment of the invention, the packed bed of ion-exchange resin is disposed within the upper region of the housing and the cyst-reducing filter element is disposed within the lower region of the housing, wherein the bottom screen is substantially parallel to the cyst-reducing filter element. Furthermore, in a preferred embodiment, the cyst-reducing filter element comprises a cellular honeycomb structure having a plurality of channels separated by porous channel walls, wherein the channels traverse the cyst-reducing filter element from a filter inlet end to a filter outlet end, and include a first plurality of channels open only at the inlet end and a second plurality of channels open only at the outlet end, and where the cellular honeycomb structure is made of ceramic. In an alternative embodiment, the cellular ceramic honeycomb structure further comprises activated carbon.
In another aspect of the invention, the cyst-reducing filter cartridge is provided where the bottom screen is attached to the housing in a slanted fashion, providing the first chamber with a low area underneath the ceiling at one end and a high area underneath the ceiling at an opposite end, and wherein the air vent conduit is disposed within the upper region and at a peripheral surface of the packed bed of ion-exchange resin, wherein the entry end of the air vent conduit opens into the high area underneath the ceiling of the first chamber, with the air vent conduit being on the same side of the housing as the gooseneck conduit. In yet another aspect of the invention, the cyst-reducing filter element is secured slantingly in the housing at a similar angle as the bottom screen.
Further yet, in another aspect of the invention, a cyst-reducing filter cartridge is provided that includes a bottom screen that has a convex shape with respect to a topmost surface of the cyst-reducing filter element, with the bottom screen providing the first chamber with a high area underneath the ceiling in the middle and a low area underneath the ceiling at the periphery, and wherein the air vent conduit is disposed in the middle of the packed bed of ion-exchange resin, with the entry end of the air vent conduit opening into the high area underneath the ceiling of the first chamber.
Furthermore, in yet another aspect of the invention, a cyst-reducing filter cartridge is provided that includes a packed bed of ion-exchange resin that is smaller in circumferential size than the filter housing, and where the packed bed of ion-exchange resin is surrounded by a resin holder screen that is water impermeable and is attached to the housing. Further, the bottom screen is concave in shape with respect to the topmost surface of the cyst-reducing filter element and is attached at the periphery to the bottom of the resin holder screen. The bottom screen is water permeable and provides the first chamber with a low area underneath the ceiling in the middle and a high area underneath the ceiling at the periphery.
In yet another embodiment of the invention, a cyst-reducing filter cartridge is provided that includes a packed bed of ion-exchange resin that is smaller in circumferential size than the filter housing, and where the packed bed of ion-exchange resin is surrounded by a resin holder screen that is water permeable and is attached to the housing. Further, the bottom screen is concave in shape with respect to the topmost surface of the cyst-reducing filter element and is attached at the periphery to the bottom of the resin holder screen. The bottom screen is water impermeable and provides the first chamber with a low area underneath the ceiling in the middle and a high area underneath the ceiling at the periphery. Further, the cartridge includes a water permeable screen conduit that traverses the center of the packed bed of ion-exchange resin. The water permeable screen conduit has an open end at the top that is adapted for receiving a stream of untreated water and an opposite closed end that is proximate to the bottom screen.
Furthermore, in yet another embodiment of the invention, a cap for sealing the top rim of a cyst-reducing filter cartridge is provided. The cap comprises a plurality of untreated water inlet ports that are located on both a raised top surface of the cap and along the bottom periphery of a side skirt extending from the cap. The cap further includes a baffle plate that is attached to the inside of the raised top surface of the cap, wherein approximately half the number of the untreated water inlet ports are located on each side of the baffle plate.
Finally, in another embodiment of the invention, a cyst-reducing water filtration device is provided that comprises the cyst-reducing filter cartridge in accordance with the present invention. The water filtration device further comprises a water filter carafe having a pour spout, and where the filter cartridge is mounted in a receptacle located in an untreated water reservoir of the filter carafe. the filter cartridge includes a housing that further comprises a top rim, a side surface, a bottom surface, and a cap that is sealingly attached to the top rim, wherein the cap comprises a plurality of untreated water inlet ports. The filter housing further comprises a gooseneck conduit that is connected to a lower region of the filter housing, wherein the gooseneck conduit has at one end a treated water outlet port that opens into the side surface of the filter housing. The filter housing further includes a packed bed of ion-exchange resin that is disposed in the filter housing and a high surface area cyst-reducing filter element that is also disposed in the filter housing. The filter element provides at least 99.95% removal of 3-4 xcexcm particles when tested in accordance with NSF standard 53, Drinking Water Treatment Unitsxe2x80x94Health Effects (September 1997). A bottom surface of the packed bed of ion-exchange resin is in full contact with one side of a bottom screen that is attached at the periphery to the side surface of the housing. The other side of the bottom screen forms a ceiling in a first chamber. The first chamber separates the packed bed of ion-exchange resin from the cyst-reducing filter element. The housing further comprises a second chamber proximate to the bottom surface of the filter housing, wherein the second chamber is in fluid communication with the gooseneck conduit. The housing also includes an air vent conduit that is connected to the upper region of the filter housing, wherein the air vent conduit has an entry end that opens into the first chamber and an exit end that opens to the outside of the housing. The exit end is positioned above the treated water outlet port of the gooseneck conduit and the exit end is further covered with a hydrophobic membrane. The exit end of the air vent conduit and the treated water outlet port of the gooseneck conduit is positioned on an opposite side of the filter carafe from the pour spout.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrating embodiments of the invention, and together with the description serve to explain the objects, advantages, and principles of the invention.